The Pearson marrow-pancreas syndrome (MIM 557000) is a disorder involving the hematopoietic system and the exocrine pancreas in early infancy. We have previously shown that this disease results from a defect of oxidative phosphorylation associated with deletions of the mitochondrial DNA. We present here a series of 21 cases (including 15 unreported patients) with Pearson syndrome and describe mitochondrial DNA deletions as consistent features in this syndrome. Nine patients presented the same 4.9 kb deletion, while other patients presented different deletions ranging in size from 9 to 14 kb between tRNACyst and the D-loop. Direct repeats (4-13 bp) were consistently present in the wild-type mtDNA at the boundaries of the deletions. Deletion-dimers, deletion-multimers or duplications were observed in association with deletions. Duplications were identified both in patients who died of their Pearson syndrome and in the ones who survived and developed Kearns-Sayre syndrome, suggesting that no correlation could be made between the clinical severity and the type, size or location of the rearrangements.

Pearson's marrow-pancreas syndrome (McKusick No. 26056) is a fatal disorder of hitherto unknown etiology involving the hematopoietic system, exocrine pancreas, liver, and kidneys. The observation of high lactate/pyruvate molar ratios in plasma and abnormal oxidative phosphorylation in lymphocytes led us to postulate that Pearson's syndrome belongs to the group of mitochondrial cytopathies. Since rearrangements of the mitochondrial genome between direct DNA repeats were consistently found in all tissues tested, our results show that this disease is in fact a multisystem mitochondrial disorder, as suggested by the clinical course of the patients. Based on these observations, we would suggest giving consideration to the hypothesis of a defect of oxidative phosphorylation in elucidating the origin of other syndromes, especially those associated with an abnormal oxidoreduction status in plasma.

In the past decade, we have studied four unrelated children with what we believe is a previously unreported disorder affecting the bone marrow and exocrine pancreas. During infancy these patients had the onset of severe, transfusion-dependent, macrocytic anemia plus a variable degree of neutropenia and thrombocytopenia. Their bone marrows had normal cellularity but were characterized by remarkable vacuolization of erythroid and myeloid precursors, hemosiderosis, and ringed sideroblasts. The vacuoles probably represented manifestations of cellular degeneration and death. In two patients, in vitro bone marrow cultures showed abnormal erythroid and myeloid progenitor cell growth and, in one child, abnormal vacuolated erythroid colonies. Family histories were unrevealing, parents were hematologically normal, and both sexes were involved. There was no evidence of specific nutritional deficiencies or exposure to agents associated with marrow vacuolization. A number of therapeutic interventions produced no effect. One child had clinical malabsorption. This child and one other had extensive pancreatic fibrosis at autopsy. The other two patients had findings indicating exocrine pancreatic dysfunction. Two children had splenic atrophy. This new syndrome, with associated bone marrow and exocrine pancreatic dysfunctions, differs in several respects from the syndrome of pancreatic liposis and neutropenia described by Shwachman et all and Bodian et al, and from other conditions with vacuolization of the marrow or sideroblastosis.